The brachial plexus is a network of nerves in the neck and shoulder region (see the diagram below). It is made up from 5 large nerves which come out of the spinal cord between the vertebrae (bones in the neck), pass under the clavicle (collar bone) and into the upper arm. These nerves enable the signals that allow movement and feeling to reach the arm. These nerves are represented in speech and writing by these symbols: C5, C6, C7, C8, T1 (C=cervical, T=thoracic)
Nerves are cord like structures of tissue formed from a collection of nerve fibers. A single nerve may contain thousands of fibers (a bit like an electrical cable). In the arm, these fibers carry electrical messages both ways between the brain, muscles and tissues. For a muscle to work (contract), a message must travel from the brain, along a nerve that goes directly to the muscle. When nerve fibers are injured, the muscles that the nerve controls may be weakened, even though the injury is not in the muscle itself.
The nervous system integrates all body activities by sensing changes (sensory function), interpreting those (integrative function) and reacting to them (motor function). Sensory neurons carry sensory information into the brain and spinal cord. Motor neurons carry information from the brain and spinal cord into the peripheral nerves. A neuron (or nerve cell) processes and transmits information by electrical or chemical signaling.
Damage to the upper nerves that make up the brachial plexus tends to occur when your shoulder is forced down while your neck stretches up and away from the injured shoulder. The lower nerves are more likely to be injured when your arm is forced above your head. These injuries can occur in several ways, including:
Many factors affect how severe the injury to the brachial plexus may be. These depend on:
We may be able to determine the degree of damage to the nerves by examining you. However, it is quite common for other tests to be done to help tell us where the nerve injury is and how bad it is. These tests may include: